Expansion valve

ABSTRACT

To provide an expansion valve which is capable of preventing the temperature of refrigerant compressed by a compressor from becoming too high, when a refrigeration load on a refrigeration cycle using an internal heat exchanger is high. A thermostatic expansion valve is applied to a refrigeration cycle provided with an internal heat exchanger that performs heat exchange between high-temperature refrigerant flowing from a condenser to the expansion valve and low-temperature refrigerant flowing from an evaporator to a compressor via the expansion valve. The expansion valve comprises a bypass passage or for causing refrigerant in a high-pressure refrigerant inlet or a low-pressure refrigerant outlet to flow to the downstream side of a temperature-sensing section, such that moist refrigerant is mixed with refrigerant whose degree of superheat is controlled by the expansion valve. This lowers the temperature of refrigerant that is drawn into the compressor when refrigeration load is high is lowered, to thereby prevent the temperature of refrigerant compressed by the compressor from becoming too high.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority of Japanese Application No. 2006-060813 filed on Mar. 7, 2006 and entitled “Expansion Valve”.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to an expansion valve, and more particularly to a thermostatic expansion valve that controls the flow rate of refrigerant to be supplied to an evaporator, according to a temperature and a pressure at an outlet of the evaporator in a refrigeration cycle of an automotive air conditioner.

(2) Description of the Related Art

From the viewpoint of environmental problems concerning global warming, it is proposed to use carbon dioxide in place of a CFC substitute (HFC-134a), as refrigerant in a refrigeration cycle for an automotive air conditioner. In the system of the refrigeration cycle using carbon dioxide as refrigerant, to enhance efficiency, an internal heat exchanger is generally used (see e.g. Japanese Unexamined Patent Publication No. 2001-108308).

The internal heat exchanger is configured such that heat exchange is performed between refrigerant flowing through a path extending from a gas cooler that cools high-temperature, high-pressure refrigerant compressed by a compressor, to an expansion valve, and refrigerant flowing through a path extending from an accumulator to the compressor. With this configuration, gaseous-phase refrigerant drawn from the accumulator is superheated by the refrigerant flowing through the path on the high-pressure side of the internal heat exchanger, and then is delivered to the compressor. This enables the compressor to draw in dry refrigerant, and hence operate efficiently.

In contrast, also in a refrigeration cycle using HFC-134a as refrigerant, it is contemplated to employ a system incorporating the internal heat exchanger. Improved efficiency is expected from such a system as well.

However, in the refrigeration cycle using HFC-134a as refrigerant, a thermostatic expansion valve is generally used as an expansion valve. The thermostatic expansion valve controls refrigerant at the outlet of an evaporator such that it has a predetermined degree of superheat. As a result, in a refrigeration cycle provided with an internal heat exchanger such that heat exchange is performed between refrigerant flowing through a path extending from a condenser to the expansion valve, and refrigerant flowing through a path extending from the evaporator to the compressor, refrigerant already superheated at the outlet of the evaporator is further superheated by the internal heat exchanger and then is delivered to the compressor, so that particularly when the refrigeration cycle is being operated in a state of the refrigeration load being high, there arises a problem of the temperature of refrigerant compressed by the compressor becoming too high to causes deterioration of lubricating oil in the compressor by the high temperature.

SUMMARY OF THE INVENTION

The present invention has been made in view of the problem, and an object thereof is to provide an expansion valve which is capable of preventing the temperature of refrigerant compressed by a compressor from becoming too high, when a refrigeration load on a refrigeration cycle using an internal heat exchanger is high.

To solve the above problem, according to the present invention, there is provided a thermostatic expansion valve that is configured to control a flow rate of refrigerant delivered to an evaporator by causing a temperature-sensing section to sense a temperature and a pressure of refrigerant having flowed out from an evaporator, comprising a bypass passage formed between a high-pressure refrigerant inlet to which high-pressure refrigerant is supplied or a low-pressure refrigerant outlet from which low-pressure refrigerant is delivered to the evaporator, and a refrigerant passage that passes the refrigerant having flowed out from the evaporator, for passing high-pressure liquid refrigerant or low-pressure gas-liquid mixed refrigerant to a downstream side of the temperature-sensing section.

The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a system diagram of a refrigeration cycle to which is applied an expansion valve according to the present invention.

FIG. 2 is a central longitudinal cross-sectional view of the construction of an expansion valve according to a first embodiment.

FIG. 3 is a central longitudinal cross-sectional view of the construction of an expansion valve according to a second embodiment.

FIG. 4 is a central longitudinal cross-sectional view of the construction of an expansion valve according to a third embodiment.

FIG. 5 is a central longitudinal cross-sectional view of the construction of an expansion valve according to a fourth embodiment.

FIG. 6 is a central longitudinal cross-sectional view of the construction of an expansion valve according to a fifth embodiment.

FIG. 7 is a central longitudinal cross-sectional view of the construction of an expansion valve according to a sixth embodiment.

FIG. 8 is a central longitudinal cross-sectional view of the construction of an expansion valve according to a seventh embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described in detail based on examples in which they are applied to a refrigeration cycle using HFC-134a as refrigerant and including an internal heat exchanger.

FIG. 1 is a system diagram showing a refrigeration cycle to which an expansion valve according to the present invention is applied.

The refrigeration cycle comprises a compressor 1 that compresses refrigerant, a condenser 2 that condenses the compressed refrigerant, an expansion valve 3 that throttles and expands cooled refrigerant, and an evaporator 4 that evaporates the expanded refrigerant. Further, the refrigeration cycle includes an internal heat exchanger 5 that performs heat exchange between refrigerant flowing from the condenser 2 to the expansion valve 3 and refrigerant flowing from the evaporator 4 to the compressor 1 via the expansion valve 3.

The expansion valve 3 is a so-called thermostatic expansion valve that has a temperature-sensing section for sensing the temperature and pressure of refrigerant having flowed out from the evaporator 4, and is configured to control the flow rate of refrigerant delivered to the evaporator 4 according to the temperature and pressure of refrigerant, sensed by the temperature-sensing section. The expansion valve 3 according to the present invention internally includes a bypass passage 3 a (indicated by arrows of solid lines) for causing high-pressure liquid refrigerant delivered from the internal heat exchanger 5 to flow to a downstream side of the temperature-sensing section, or a bypass passage 3 b (indicated by a arrow of a broken line) for causing low-pressure gas-liquid mixed refrigerant delivered to the evaporator 4 to flow to the downstream of the temperature-sensing section. Next, a description will be given of details of the construction of the expansion valve 3.

FIG. 2 is a central longitudinal cross-sectional view of the construction of the expansion valve according to a first embodiment.

The expansion valve 10 according to the first embodiment has a body 11 a side of which is formed with a high-pressure refrigerant inlet 12 into which high-temperature, high-pressure liquid refrigerant is delivered from the internal heat exchanger 5, a low-pressure refrigerant outlet 13 from which low-temperature, low-pressure liquid throttled and expanded by the expansion valve 10 is delivered to the evaporator 4, a refrigerant passage inlet 14 for receiving evaporated refrigerant from the evaporator 4, and a refrigerant passage outlet 15 for delivering refrigerant having passed through the expansion valve 10 to the internal heat exchanger 5.

A valve seat 16 is integrally formed with the body 11 in a passage communicating between the high-pressure refrigerant inlet 12 and the low-pressure refrigerant outlet 13, and a ball-shaped valve element 17 is disposed on the upstream side of the valve seat 16. A valve element receiver 18 for receiving the valve element 17, and a compression coil spring 19 that urges the valve element 17 via the valve element receiver 18 in a direction in which the valve element 17 is seated on the valve seat 16 are arranged in a space accommodating the valve element 17. A lower end, as viewed in FIG. 1, of the compression coil spring 19 is received by a spring receiver 20 which is fitted into an adjustment screw 21 screwed into a lower end of the body 11. The adjustment screw 21 has a function of adjustmenting the load of the compression coil spring 19 by adjusting the amount of screwing itself into the body 11.

Further, the expansion valve 10 has a temperature-sensing section provided in an upper end of the body 11. The temperature-sensing section comprises an upper housing 22, a lower housing 23, a diaphragm 24 disposed in a manner dividing a space enclosed by the housings, and a disk 25 disposed below the diaphragm 24.

A shaft 26 is disposed below the disk 25 for transmitting the displacement of the diaphragm 24 to the valve element 17. An upper portion of the shaft 26 is held by a holder 28 disposed extending across a refrigerant passage 27 communicating between the refrigerant passage inlet 14 and the refrigerant passage outlet 15. A compression coil spring 29 giving lateral load to an upper end of the shaft 26 is disposed in the holder 28 so as to suppress the vibration of the shaft 26 in the longitudinal direction thereof, caused by fluctuations in the pressure of high-pressure refrigerant.

The body 11 is formed with a bypass passage 30 through which the high-pressure refrigerant delivered into the body 11 bypasses the expansion valve 10. The bypass passage 30 is formed between the high-pressure refrigerant inlet 12 into which the high-pressure liquid refrigerant is delivered, and the refrigerant passage 27, and has a differential pressure control valve inserted in an intermediate portion thereof. The differential pressure control valve comprises a valve seat 31, a valve element 32 disposed on the downstream side of the valve seat 31 in opposed relation thereto in a manner movable to and away therefrom, a compression coil spring 33 urging the valve element 32 in the valve-closing direction, and a spring receiver 34 press-fitted into the bypass passage 30 for receiving the compression coil spring 33. The bar-shaped valve element 32 has a plurality of communication grooves formed in an outer periphery thereof such that they extend in the longitudinal direction, and when the differential pressure control valve is opened, the high-pressure liquid refrigerant flows through the communication grooves.

The expansion valve 10 configured as above senses the pressure and temperature of refrigerant returning from the evaporator 4 to the refrigerant passage inlet 14. When the temperature of the refrigerant is high or the pressure thereof is low, the diaphragm 24 is displaced downward, as viewed in FIG. 2, and the displacement is transmitted to the valve element 17 via the shaft 26 to thereby move the valve element 17 in the valve-opening direction, whereas when the temperature of the refrigerant is low or the pressure thereof is high, the valve element 17 is caused to move in the valve-closing direction, whereby the opening degree of the expansion valve 10 is controlled to control the flow rate of refrigerant to be delivered to the evaporator 4. The expansion valve 10 controls the flow rate of refrigerant to be delivered to the evaporator 4 by sensing the temperature of refrigerant in the outlet of the evaporator 4, to thereby control refrigerant flowing from the evaporator 4 into the refrigerant passage inlet 14 such that it has a predetermined degree of superheat.

On the other hand, liquid refrigerant delivered from the evaporator 4 into the refrigerant passage inlet 14 is mixed with superheated refrigerant passing through the refrigerant passage 27, via the bypass passage 30. The bypassing amount of the liquid refrigerant is controlled according to the differential pressure between pressure in the high-pressure refrigerant inlet 12 and pressure in the refrigerant passage 27. When the refrigeration load is low, the differential pressure between discharge pressure and suction pressure in the compressor 1 is low, and hence the differential pressure between the pressure in the high-pressure refrigerant inlet 12 and the pressure in the refrigerant passage 27 is also low, whereby the differential pressure control valve inserted in the bypass passage 30 is closed. In such a case, the liquid refrigerant is inhibited from directly flowing into the downstream side of the temperature-sensing section. This is because when the refrigeration load is low, the temperature of refrigerant compressed by the compressor 1 is not very high.

When the refrigeration load is high, the differential pressure between the discharge pressure and the suction pressure in the compressor 1 increases and the differential pressure between the pressure in the high-pressure refrigerant inlet 12 and the pressure in the refrigerant passage 27 also increase, so that when the differential pressure across the differential pressure control valve becomes equal to a predetermined value (e.g. 1.3 MPa) or higher, the differential pressure control valve opens against the urging force of the compression coil spring 33 to cause the liquid refrigerant to flow into the downstream side of the temperature-sensing section and get mixed with the liquid refrigerant in the superheated state. This lowers the temperature of the refrigerant in the superheated state to thereby change the mixture into moist refrigerant. The internal heat exchanger 5 causes such refrigerant to exchange heat with lowered-temperature refrigerant from the condenser 2, whereby the refrigerant undergoes evaporation and is superheated, and the superheated refrigerant is drawn into the compressor 1. Therefore, the temperature of refrigerant drawn into the compressor 1 is prevented from becoming too high, which prevents the temperature of refrigerant compressed by the compressor 1 from becoming too high. This prevents thermal deterioration of lubricating oil in the compressor 1, which circulates together with refrigerant through the refrigeration cycle.

FIG. 3 is a central longitudinal cross-sectional view of the construction of an expansion valve according to a second embodiment. In FIG. 3, component elements identical to those shown in FIG. 2 are designated by identical reference numerals, and detailed description thereof is omitted.

As is distinct from the expansion valve 10 according to the first embodiment in which the differential pressure control valve is inserted in the bypass passage 30, the expansion valve 40 according to the second embodiment is characterized in that the bypass passage 30 is provided with an orifice 35 having a very small degree of opening. According to the expansion valve 40 configured as above, liquid refrigerant always flows though the bypass passage 30. Therefore, although the temperature of refrigerant delivered to the internal heat exchanger 5 can be too low when the refrigeration load is low, it is possible to reduce costs compared with the expansion valve 10 according to the first embodiment.

FIG. 4 is a central longitudinal cross-sectional view of the construction of an expansion valve according to a third embodiment. In FIG. 4, component elements identical to those shown in FIG. 2 are designated by identical reference numerals, and detailed description thereof is omitted.

As is distinct from the expansion valve 10 according to the first embodiment in which the bypass passage 30 is formed between the high-pressure refrigerant inlet 12 and the refrigerant passage 27, the expansion valve 50 according to the third embodiment is characterized in that the bypass passage 30 is formed through the body 11 between the low-pressure refrigerant outlet 13 and the refrigerant passage 27.

In the expansion valve 50, although the differential pressure control valve is inserted in the bypass passage 30, the spring load of the compression coil spring 33 is set such that the differential pressure control valve is opened when the differential pressure thereacross is not lower than a predetermined value of e.g. 0.03 MPa. With this configuration, when the refrigeration load is low, the flow rate of refrigerant flowing through the evaporator 4 is low, and hence the differential pressure between pressure in the inlet of the evaporator 4 and pressure in the outlet thereof is also low, and moreover the differential pressure is approximately equal to the differential pressure across the differential pressure control valve inserted in the bypass passage 30, so that the differential pressure control valve is closed. As a result, when high-pressure liquid refrigerant passes through a clearance between the valve element 17 and the valve seat 16, all the gas-liquid mixed refrigerant expanded at the low-pressure refrigerant outlet 13 is delivered to the evaporator 4, and is inhibited from directly flowing into the downstream side of the temperature-sensing section.

When the refrigeration load is high, the flow rate of refrigerant flowing through the evaporator 4 is high, and hence the differential pressure between the pressure in the inlet of the evaporator 4 and the pressure in the outlet thereof becomes high, that is, the differential pressure across the differential pressure control valve is increased. When the differential pressure becomes equal to the predetermined value or higher, the differential pressure control valve opens against the urging force of the compression coil spring 33 to cause the liquid refrigerant to flow into the downstream side of the temperature-sensing section and get mixed with the refrigerant in the superheated state. As a result, the temperature of refrigerant drawn into the compressor 1 is prevented from becoming too high, which also prevents the temperature of refrigerant compressed by the compressor 1 from becoming too high. This also prevents thermal deterioration of lubricating oil in the compressor 1.

FIG. 5 is a central longitudinal cross-sectional view of the construction of an expansion valve according to a fourth embodiment. In FIG. 5, component elements identical to those shown in FIG. 3 are designated by identical reference numerals, and detailed description thereof is omitted.

Similarly to the expansion valve 40 according to the second embodiment, the expansion valve 60 according to the fourth embodiment has the orifice 35 formed in the bypass passage 30. According to the expansion valve 60 configured as above, gas-liquid mixed refrigerant is always allowed to flow though the bypass passage 30. As described above, gas-liquid mixed refrigerant is mixed with refrigerant flowing through the refrigerant passage, thereby lowering the temperature of refrigerant delivered to the internal heat exchanger 5, which prevents the temperature of refrigerant compressed by the compressor 1 from becoming too high.

FIG. 6 is a central longitudinal cross-sectional view of the construction of an expansion valve according to a fifth embodiment. In FIG. 6, component elements identical to those shown in FIG. 2 are designated by identical reference numerals, and detailed description thereof is omitted.

In the expansion valve 70 according to the fifth embodiment, the bypass passage 30 is formed by a through hole which is formed through the body 11 such that the shaft 26 disposed between the temperature-sensing section and the valve element 17 is inserted therethrough. In the bypass passage 30, the valve element 32 of the differential pressure control valve is axially movably disposed as a guide for the shaft 26, and the compression coil spring 33 is disposed between the valve element 32 and the holder 28, for urging the valve element 32 in a direction in which the valve element 32 is seated on the valve seat 31 formed by a stepped portion in the bypass passage 30.

When compared to the expansion valve 50 of FIG. 4 according to the third embodiment, the expansion valve 70 is different therefrom only in the location of the bypass passage 30 and has the differential pressure control valve disposed in the bypass passage 30, which opens when the differential pressure thereacross becomes equal to the predetermined value or higher. Therefore, the expansion valve 70 operates in quite the same manner.

Further, although an opening, through which refrigerant is supplied from the bypass passage 30 to the refrigerant passage 27, is disposed at a location of the refrigerant passage 27, opposed to the temperature-sensing section, low-temperature gas-liquid mixed refrigerant that has been supplied from the bypass passage 30 to the refrigerant passage 27 through the differential pressure control valve is immediately carried away toward the refrigerant passage outlet 15 by refrigerant from the evaporator 4, so that the gas-liquid mixed refrigerant is mixed with refrigerant returning from the evaporator 4 on the downstream side of the temperature-sensing section, without the temperature thereof being sensed by the temperature-sensing section.

FIG. 7 is a central longitudinal cross-sectional view of the construction of an expansion valve according to a sixth embodiment. In FIG. 7, component elements identical to those shown in FIG. 3 are designated by identical reference numerals, and detailed description thereof is omitted.

In the expansion valve 80 according to the sixth embodiment, the bypass passage 30 is formed by a through hole formed through the body 11 such that the shaft 26 disposed between the temperature-sensing section and the valve element 17 is inserted therethrough, and has the orifice 35 formed in an intermediate portion thereof. The expansion valve 80 is substantially identical with the expansion valve 60 of FIG. 5 according to the fourth embodiment, in respect of construction in which moist refrigerant is always mixed with superheated refrigerant that is delivered from the evaporator 4, by utilizing the differential pressure between the pressure in the inlet of the evaporator 4 and the pressure in the outlet thereof, and therefore the expansion valve 80 operates in the same manner as the expansion valve 60.

FIG. 8 is a central longitudinal cross-sectional view of the construction of an expansion valve according to a seventh embodiment. In FIG. 8, component elements identical to those shown in FIG. 4 are designated by identical reference numerals, and detailed description thereof is omitted.

The expansion valve 90 according to the seventh embodiment is applied to a refrigeration cycle that employs a double tube 36 as a pipe on the side toward the compressor 1 and the condenser 2. The double tube 36 is formed by coaxially arranging an outer tube 36 a and an inner tube 36 b, and since refrigerant flowing through the outer tube 36 a and refrigerant flowing through the inner tube 36 b are separated by the inner tube 36 b, the double tube 36 has the function of the internal heat exchanger 5.

The expansion valve 90 has the high-pressure refrigerant inlet 12, into which high-temperature, high-pressure liquid refrigerant is delivered from the condenser 2, disposed on a side from which the valve element 17 is opened, and the compression coil spring 19 and the spring receiver 20 disposed on the downstream side of the valve element 17. The bypass passage 30 is formed between a low-temperature, low-pressure chamber where the valve element 17 is disposed, and the refrigerant passage 27 through which refrigerant returning from the evaporator 4 passes. The valve element 32 held on the shaft 26 in a manner movable in the directions of opening and closing the bypass passage 30 is disposed at an open end of the bypass passage 30 opening into the refrigerant passage 27. The valve element 32 is urged by the compression coil spring 33 in the direction in which the valve element 32 is seated on the valve seat 31, to thereby form a differential pressure control valve.

The high-temperature, high-pressure liquid refrigerant delivered from the outer tube 36 a of the double tube 36 into the high-pressure refrigerant inlet 12 is throttled and expanded into low-temperature, low-pressure refrigerant when passing through the clearance between the valve element 17 and the valve seat 16, and is delivered from the low-pressure refrigerant outlet 13 to the evaporator 4. Refrigerant returning from the evaporator 4 is received by the refrigerant passage inlet 14, and passes through the refrigerant passage 27 to be delivered from the refrigerant passage outlet 15 to the inner tube 36 b of the double tube 36. At this time, the temperature-sensing section senses the temperature and pressure of the refrigerant passing through the refrigerant passage 27, to control the flow rate of refrigerant to be delivered to the evaporator 4.

Further, the differential pressure control valve disposed in the bypass passage 30 senses the differential pressure between the pressure of refrigerant in the low-pressure refrigerant outlet 13 and the pressure of refrigerant in the refrigerant passage 27, to control the flow rate of refrigerant passing from the low-pressure refrigerant outlet 13 to the refrigerant passage 27. Although an opening, through which refrigerant is supplied from the bypass passage 30 to the refrigerant passage 27, is formed at a location of the refrigerant passage 27, opposed to the temperature-sensing section, low-temperature gas-liquid mixed refrigerant that has been supplied from the bypass passage 30 to the refrigerant passage 27 through the differential pressure control valve is carried away toward the refrigerant passage outlet 15 by refrigerant evaporated by the evaporator 4, so that the temperature of the gas-liquid mixed refrigerant is not sensed by the temperature-sensing section.

Although in the above-described embodiments, the descriptions have been given of the examples in which they are applied to the refrigeration cycle having the internal heat exchanger and using HFC-134a as refrigerant, the present invention can also be applied to a refrigeration cycle that uses another refrigerant with a small global warming coefficient and similar physical properties.

The expansion valve according to the present invention is configured such that moist refrigerant is caused to flow through the bypass passage to a downstream side of the temperature-sensing section. Therefore, when the present invention is applied to the refrigeration cycle employing the internal heat exchanger, it is possible to lower the temperature of refrigerant to be delivered to the compressor via the heat exchanger. This makes it possible to prevent the temperature of refrigerant compressed by the compressor under a high refrigeration load condition from becoming too high to thereby prevent thermal deterioration of the lubricating oil in the compressor.

The foregoing is considered as illustrative only of the principles of the present invention. Further, since numerous modifications and change will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and applications shown and described, and accordingly, all suitable modifications and equivalents may be regarded as falling within the scope of the invention in the appended claims and their equivalents. 

1. A thermostatic expansion valve that is configured to control a flow rate of refrigerant to be delivered to an evaporator by causing a temperature-sensing section to sense a temperature and a pressure of refrigerant having flowed out from an evaporator, comprising: a bypass passage formed between a high-pressure refrigerant inlet to which high-pressure refrigerant is supplied or a low-pressure refrigerant outlet from which low-pressure refrigerant is delivered to the evaporator, and a refrigerant passage that passes the refrigerant having flowed out from the evaporator, for passing high-pressure liquid refrigerant or low-pressure gas-liquid mixed refrigerant to a downstream side of said temperature-sensing section.
 2. The expansion valve according to claim 1, wherein said bypass passage is an orifice formed through a body between said high-pressure refrigerant inlet and said refrigerant passage.
 3. The expansion valve according to claim 1, wherein said bypass passage has a differential pressure control valve that opens when a differential pressure thereacross becomes not lower than a predetermined value, in a passage formed through a body between said high-pressure refrigerant inlet and said refrigerant passage.
 4. The expansion valve according to claim 1, wherein said bypass passage is an orifice formed through a body between said low-pressure refrigerant outlet and said refrigerant passage.
 5. The expansion valve according to claim 1, wherein said bypass passage has a differential pressure control valve that opens when a differential pressure thereacross becomes not lower than a predetermined value, in a passage formed through a body between said low-pressure refrigerant outlet and said refrigerant passage.
 6. The expansion valve according to claim 1, wherein said bypass passage is a through hole formed through a body such that a shaft is inserted therethrough, said shaft being disposed between said temperature-sensing section and a valve element that controls the flow rate of refrigerant delivered to the evaporator.
 7. The expansion valve according to claim 1, wherein said bypass passage has a differential pressure control valve that opens when a differential pressure thereacross becomes not lower than a predetermined value, in a through hole formed through a body such that a shaft is inserted therethrough, said shaft being disposed between said temperature-sensing section and a valve element that controls the flow rate of refrigerant delivered to the evaporator.
 8. The expansion valve according to claim 1, which is applied to a refrigeration cycle provided with an internal heat exchanger that performs heat exchange between refrigerant having flowed out from a condenser and refrigerant being drawn into a compressor. 